In packaging or sorting articles in a stack, an infeed of the articles in the form of a stack is passed to a strip feeder which strips or shears a certain number of articles from the bottom of the feed stack or the leading edge of the feed stack. Stripping the articles from the feed stack comprises shearing the article stack by a stripper means, including, for example, a strip feeder having a stripper lug to shear the desired number of articles from the feed stack for packaging. In this fashion, the stripper lug “picks” a desired number of articles from a feed stack. However, the stack of articles removed by a typical strip feeder is limited in size by a fixed guide means positioned to allow the stripper means to pass just underneath of the guide, thereby shearing articles from a feed stack. Thus, a typical strip feeder provides a specific stack height which matches a preset number of articles to be packaged in a “one size fits all” fashion. Accordingly, if the articles become thicker over time, the strip feeder will break articles that impinge against the bottom or side of the fixed guide means, will successfully strip fewer than the desired number of articles from the infeed, and may cause jamming in the feed stack. Where the articles tend to become thinner over time, the stripper lug will tend to shear more than a desired number of articles from a feed stack, or break articles that abut the fixed guide means during stripping. In addition, the breakage of articles from a feed stack invariably results in the clogging and stoppage of a packaging or sorting assembly which causes time delays and greatly adds to the expense of processing and packaging the stacked articles.
In a typical packaging operation, a single packaging or sorting assembly comprises multiple infeed lines. Often product thicknesses vary between the different infeed lines in a given packaging assembly. For example, for baked crackers, cookies, and biscuits, the actual thickness of the product will vary across the width of an oven band so that the product on the edges of an oven are thinner than the product in the center of the oven where leavening or where thermal expansion is maximized. An infeed and packaging assembly can be adapted to package only that series of cookies, crackers or biscuits which are baked in a specific row or lane of the oven so that, for instance, only the crackers, cookies or biscuits which are baked adjacent the left-hand side of the oven are packaged in a specific product infeed and packaging assembly. However, each new batch of dough will result in a slightly different product differing in thickness from the product of the previous batch. Accordingly, even an infeed and packaging assembly which is arranged to package a specific row of product will ultimately break down or fail in shearing a desired number of product articles from an infeed stack due to changes in thickness in the articles.
To minimize damage to a feed stack of articles, a strip feeder can be set to pick only a small number of articles from the feed stack to send to further processing. However, a packaging or sorting assembly for cookies, crackers or biscuits, for example, usually is adapted to package ten or more of such articles in a “slug”. In such an instance, the stack of articles moved by a typical strip feeder does not strip enough articles to make up the slug. As a result, several strip feeders must be arranged within a packaging assembly that feeds a given wrapper. For example, three strip feeders can be arranged upstream of a single wrapper so that three separate “stripped” stacks of articles can then be combined to make a single “slug” or stack of articles for wrapping or sorting. However, any time one of the feed stacks or strip feeders clogs or breaks down, it will idle the entire assembly feeding a given wrapper, no matter whether there is a problem in the other feed stacks or strip feeders.
An infeed supply problem also results when a strip feeder assembly having three strip feeders is designed to create a slug having ten articles in a stack. In such an example, two of the strip feeders will pick three articles from a feed stack and one of the strip feeders will pick four articles from a feed stack. As a result, the backlog or supply of articles in the infeed supplying the strip feeder which picks four articles will run out of product before the backlog or supply of articles in the infeed for the two strip feeders set to pick three articles. Accordingly, it is necessary to set the strip feed assembly to pick four articles from alternating stacks. A conventional shifter shifts a stack support downwardly so as to permit four articles, instead of three, to pass under the stack guide means and be picked from the stack. An article sensor system comprising photoelectric eyes or vision technology may be used to sense or detect the extent of backup or supply of shingled articles on the conveyor system upstream of the shifter for automatically determining when the shift should be made for each line.
The automatic shifting to change the number of articles picked from the stack is by a pre-fixed amount, which may be equal to or slightly greater than the average article thickness. However, with a conventional shifter, the amount shifted is not adjusted for any changes in thickness of the individual articles. Accordingly, a change in article thickness may result in jamming or product breakage when the shifter is set for picking either of its two preset number of articles, e.g. when the shifter is set for either three or four articles. Also, resetting the article picking clearance to fit a change in article thickness for a given number of articles, would not automatically correct or proportionally change the clearance for another given number of articles where the amount of shift is pre-fixed or preset. Moreover, with a conventional shifter, to change the amount of shift, each line feeding the wrapper would have to be shut down for a substantial period of time thereby idling production.
The present invention provides a strip feeder system in a packaging or sorting assembly which allows the user to adapt the system to “pick” a desired number of articles having a thickness which changes over time from an article feed. The strip feeder system allows one to switch the number of articles picked from an article infeed stream to a different number during processing while automatically proportionally compensating for changes in article thickness. A plurality of proportional shifters are employed to switch the number of articles picked by a strip feeder during processing and each proportional shifter is equipped with an article gauge to adjust article thickness as it changes during processing. Multiple article feed streams derived from a common source such as a band oven, may be fed via a plurality of shifters to a single wrapper, packaging or sorting assembly. Breakdowns or shutdowns in any portion of the assembly are avoided by allowing an adjustment for changes in article thickness without interrupting the flow of articles. The present invention provides a system and method for continuously packaging or sorting fragile articles such as crackers and cookies, having varying thicknesses in a stack where the individual article thickness may vary across multiple supply lines and also within a given supply line. In accordance with the present invention adjustments can be made for variation in article thickness and variation in supply line backup for a plurality of supply lines which feed a single wrapping or packaging machine while avoiding the need to shut down the supply to the packaging machine thereby substantially reducing idle time, product waste and scrap.